Leetcode 9. Palindrome Number(判断回文数字)
2016-07-31 19:31
274 查看
Determine whether an integer is a palindrome. Do this without extra space.(不要使用额外的空间)
Some hints:
Could negative integers be palindromes? (ie, -1)
If you are thinking of converting the integer to string, note the restriction of using extra space.
You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How would you handle such case?
There is a more generic way of solving this problem.
分析:
回文数,并且题目要求不能使用额外的空间。
即,不能使用回文串的方法。
本题很简单,算出x的倒置数a,比较a是否和x相等就行了。
网上其他的代码,其思路:每次提取头尾两个数,判断它们是否相等,判断后去掉头尾两个数
Some hints:
Could negative integers be palindromes? (ie, -1)
If you are thinking of converting the integer to string, note the restriction of using extra space.
You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How would you handle such case?
There is a more generic way of solving this problem.
分析:
回文数,并且题目要求不能使用额外的空间。
即,不能使用回文串的方法。
本题很简单,算出x的倒置数a,比较a是否和x相等就行了。
class Solution { public: bool isPalindrome(int x) { //算出x的倒置数a,比较a是否和x相等就行了 int a = 0, b = x; while(b > 0){ a = a * 10 + b % 10; b /= 10; } if(a == x) return true; else return false; } };
网上其他的代码,其思路:每次提取头尾两个数,判断它们是否相等,判断后去掉头尾两个数
class Solution { public: bool isPalindrome(int x) { //negative number if(x < 0) return false; int len = 1; while(x / len >= 10) len *= 10; while(x > 0) { //get the head and tail number int left = x / len; int right = x % 10; if(left != right) return false; else { //remove the head and tail number x = (x % len) / 10; len /= 100; } } return true; } };
相关文章推荐
- leetcode 9 给一个int类型的数字,判断是否是回文数
- 【leetcode】对撞指针应用之回文字符串判断(忽略大小写,以及出数字外其他字符)
- Palindrome Number 判断一个数字是否是回文数字@LeetCode
- 【LeetCode008-009算法/编程练习C++】string转int(atoi),判断数字是否是回文
- Leetcode 07 Reverse Integer(数字反转) && 09 Palindrome number(回文判断)
- LeetCode--判断一个十进制数字是否为回文
- LeetCode 9 Palindrome Number(回文数字判断)
- leetcode——Palindrome Number 判断整数数字是否为回文(AC)
- leetcode第9题,判断数字是否是回文数字的两种方法
- 判断回文数字
- 判断数字是否是回文数字(无需另外开销)
- 判断一个数字是否是回文
- 72-回文数的判断,随意的输入一个int数字,判断是不是回文数字
- 63-输入一个数字,判断是不是回文数字
- Leetcode中判断数字
- leetcode:Palindrome Number (判断数字是否回文串) 【面试算法题】
- 回文数字判断
- 判断一个字符串是否是“回文”数字
- 判断一个数字是否是回文
- leetcode:Palindrome Number (判断数字是否回文串) 【面试算法题】